1. Field of Invention
The present invention relates to a Micro-Electro-Mechanical System (MEMS) chip; particularly, it relates to such a MEMS chip having a stopper which constrains the displacement of a movable structure of the MEMS chip by a resilience force, such that the movable structure of the MEMS chip is not damaged by an undesired collision, so as to enhance the robustness of the MEMS chip.
2. Description of Related Art
Please refer to FIG. 1, which shows a schematic diagram of a conventional MEMS chip. The conventional MEMS chip 1 includes a cap wafer 10 and a substrate 3. A movable structure 2 is connected to the substrate 3 via a fixing part 6 and an anchor 7.
In the conventional MEMS chip 1 which is for example a micro-acoustical sensor, gyro-sensor, or accelerometer, etc., the internal movable structure 2 is often required to be sealed in a sealed space. When the movable structure 2 moves relatively to the substrate 3 along a direction S′, to prevent the movable structure 2 from directly collide to the cap wafer 10, a stopper 12 is often required to limit the movements of the movable structure 2. The unwanted collision of the movable structure 2 may generate particles which cause the internal pressure in the sealed space to be inaccurate, or may even cause a serious damage of the movable structure 2. In such prior art, the stopper 12 is formed during the manufacturing process as a downward projecting portion of the cap wafer 10, extending from a lower surface 10a of the cap wafer 10 toward the movable structure 2, as shown in FIG. 1. The stopper 12 has two lateral bevels 121 which overlap with the movable structure 2 (as illustrated by the dotted line in FIG. 1). The lateral bevels 121 helps to prevent the movable structure 2 from directly collide to the cap wafer 10.
However, when the movable structure 2 moves relatively to the substrate 3 along the direction S′, if a force F1′ exerted from the movable structure 2 to the stopper 12 is too strong, the movable structure 2 or the stopper 12 will still be damaged by the collision to cause the above-mentioned problems.
For relevant details, one can refer to U.S. Pat. No. 8,661,900, U.S. Pat. No. 8,124,895 and U.S. Patent Publication No. 2013/0106241.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a MEMS chip having a stopper which constrains the displacement of a movable structure of the MEMS chip by a resilience force, such that the movable structure of the MEMS chip is not damaged by an undesired collision, so as to enhance the robustness of the MEMS chip.